CN114655180A - Master cylinder pressure robust control method suitable for integrated electronic hydraulic brake system - Google Patents
Master cylinder pressure robust control method suitable for integrated electronic hydraulic brake system Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
- B60T13/745—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive acting on a hydraulic system, e.g. a master cylinder
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Abstract
The invention relates to a master cylinder pressure robust control method suitable for an integrated electronic hydraulic brake system. Constructing a robust controller for an integrated electronic hydraulic control system, and when the integrated electronic hydraulic control system is in a braking working state, acquiring braking working parameters of the integrated electronic hydraulic control system, wherein the braking working parameters comprise a state variable of micro state change near a balance point and a master cylinder pressure micro variation error of a servo master cylinder; and the robust controller determines the control input torque of the motor in the integrated electronic hydraulic control system according to the brake working parameters, so that the master cylinder pressure of a servo master cylinder in the integrated electronic hydraulic control system is matched with the wheel cylinder pressure of a brake wheel cylinder when the output torque of the motor is the determined control input torque. The invention can effectively eliminate steady-state errors, reduce the influence of uncertain factor disturbance, meet the requirements of high-performance linear braking, and is safe and reliable.
Description
Technical Field
The invention relates to a master cylinder pressure robust control method, in particular to a master cylinder pressure robust control method suitable for an integrated electronic hydraulic brake system.
Background
With the development and innovation of automobile electric control technology and computer network technology, the modern automobile industry is increasingly deepened in the process of electromotion and intellectualization. Meanwhile, due to the limitations of the working mode and response time of the conventional vacuum-assisted hydraulic brake system of the automobile, a high-performance brake-by-wire system is gradually required.
The electronic hydraulic brake system replaces part of mechanical components in the traditional hydraulic brake system with electronic components, and is the development direction of a brake-by-wire system. The electronic hydraulic brake systems are mainly classified into a pump-type electronic hydraulic brake system (P-EHB) in which an accumulator and a solenoid valve are main actuators, and an integrated electronic hydraulic brake system (I-EHB) in which a motor and a reduction mechanism are main actuators. Compared with the P-EHB, the I-EHB abandons a high-pressure accumulator and a high-speed switch control valve system thereof, saves the cost and avoids the risk of brake fluid leakage.
However, when the integrated electronic hydraulic brake system (I-EHB) operates, it is susceptible to multiple uncertain factors such as temperature, humidity, and load disturbance, and thus an oscillation phenomenon is easily generated. Therefore, the hydraulic control system is required to have strong adaptability to uncertain disturbance outside and meet index requirements, and robust control of the pressure of the servo master cylinder becomes a key point of research.
In the prior art, a document integrated electronic hydraulic brake system robust hydraulic pressure control (robust hydraulic pressure control) with a publication date of 2015 8 provides an integrated electronic hydraulic brake system robust hydraulic pressure control method by using a field method based on system improvement, so that the response speed is increased, and the system performance is optimized.
The patent application with publication number CN109760654A discloses a control method for an electronic hydraulic brake system, which is characterized in that when an ABS works, the system and the ABS cooperate to prevent the master cylinder pressure from being too large and the master cylinder pressure from fluctuating too large, thereby effectively prolonging the service life of a mechanical transmission part, a foundation brake and the ABS of the electronic hydraulic brake system, improving the brake reliability and reducing the cost.
The patent application with publication number CN112937533A discloses that electric power assistance is performed through a permanent magnet synchronous motor, a brake pedal performs mechanical power assistance, and the electric power assistance and the mechanical power assistance are separated to realize decoupling between the brake pedal and a brake master cylinder; the hydraulic control adjusts the target hydraulic pressure and the actual hydraulic pressure by establishing a pressure following controller, so that the permanent magnet synchronous motor can obtain the target torque, the brake master cylinder establishes the hydraulic pressure, and meanwhile, the actual hydraulic pressure signal is fed back to the pressure following controller, so that the positive, negative and locked rotation of the permanent magnet synchronous motor is controlled by outputting the target torque in real time, and the purposes of pressurization, depressurization and pressure maintaining are achieved.
Because the master cylinder pressure of the integrated electronic hydraulic brake system is easily disturbed by multiple uncertain factors, the existing control method can meet the actual application requirements and cannot achieve the actual high-performance linear braking purpose.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a master cylinder pressure robust control method suitable for an integrated electronic hydraulic brake system, which can effectively eliminate steady-state errors, reduce the influence of uncertain factor disturbance, meet the requirements of high-performance linear braking, and is safe and reliable.
According to the technical scheme provided by the invention, the robust control method of the master cylinder pressure suitable for the integrated electronic hydraulic brake system,
for an integrated electro-hydraulic control system, constructing a robust controller for robust control of a master cylinder pressure of the integrated electro-hydraulic control system, wherein, in constructing the robust controller, establishing Z2Model as H2Performance index, using the output of the corresponding linear state space model of the integrated electronic hydraulic control system as H∞The linear state space model is obtained by constructing a linear processing balance point based on the system state space model of the integrated electronic hydraulic control system, the linear processing of the balance point comprises the Taylor expansion processing of a nonlinear term of the system state space model, and the micro state change near the balance point is used as a state variable;
when the integrated electronic hydraulic control system is in a braking working state, obtaining braking working parameters of the integrated electronic hydraulic control system, wherein the braking working parameters comprise state variables of micro state changes at a balance point and a master cylinder pressure micro variable quantity error of a servo master cylinder; and the robust controller determines the control input torque of the motor in the integrated electronic hydraulic control system according to the brake working parameters, so that the master cylinder pressure of the servo master cylinder in the integrated electronic hydraulic control system is matched with the master cylinder pressure reference value of the servo master cylinder when the output torque of the motor is the determined control input torque.
Adding an integral link for eliminating steady-state errors into the linear state space model to obtain an augmented state space model of a balance point;
after obtaining the space model of the augmentation state, when constructing a robust controller, the output of the space model of the augmentation state is used
As H∞And controlling the index.
The integrated electronic hydraulic control system further comprises a ball screw, a plurality of control valves and a brake pipeline in adaptive connection with the control valves, wherein an output shaft of the motor is in adaptive connection with a piston rod of the servo main cylinder through the ball screw, and the brake wheel cylinder is in adaptive connection with the servo main cylinder through a brake pipeline and the corresponding control valves.
The linear state space model is:
wherein y is the small change of the master cylinder pressure of the servo master cylinder, and y is delta PsU is a minute amount of change in the current torque of the motor relative to the torque at the equilibrium point, and u is equal to u1-ueU is the current torque of the motor, ueThe motor moment is a balance point;
is the derivative of x, δ θmIs the micro-variation, deltaP, of the current angular displacement of the rotor of the motor relative to the angular displacement of the rotor at the balance pointsIs used for servo of the micro variation of the current master cylinder pressure of the master cylinder relative to the master cylinder pressure at the balance point, deltaPwA, B and C are coefficient matrixes for the minute amount of change in the current wheel cylinder pressure of the brake wheel cylinder in the operating state with respect to the wheel cylinder pressure at the equilibrium point.
The coefficient matrix a, the coefficient matrix B and the coefficient matrix C are respectively:
wherein, the first and the second end of the pipe are connected with each other,
Jmis the total equivalent moment of inertia, C, of the rotating parts in the integrated electronic hydraulic control systemmIs the damping coefficient of the motor, PhIs the lead of a ball screw, msTo servo the mass of the master cylinder piston, AsTo servo the pressure area of the master cylinder piston, AwThe sectional area of a piston of a brake wheel cylinder, beta is the volume elastic modulus of brake fluid, LsFor maximum stroke of the servo master cylinder piston, KwEquivalent stiffness of the brake disc, LwFor the initial stroke of the brake wheel cylinder piston, rho is the brake fluid density, dpTo the diameter of the brake pipe, LpFor length of brake pipe, VhFor brake fluid viscosity, k is the linearization coefficient, CdFor control valve flow coefficient, E is the effective restriction area of the control valve, L0Is the initial length of the servo master cylinder cylindrical cavity.
The space model of the augmentation state is as follows:
wherein the content of the first and second substances,
to augment the output of the state space model,
e is the error of the micro variation of the master cylinder pressure of the servo master cylinder, wherein e is r-y, r is the reference variation of the master cylinder pressure of the servo master cylinder,
when constructing a robust controller, Z is established2Model as H2The performance indexes are as follows:
wherein the content of the first and second substances,
q is a tracking performance matrix reflecting a master cylinder pressure reference value of the servo master cylinder, and R is an input value energy matrix reflecting an input value.
H is to be2/H∞The state feedback robust control is solved by using an LMI mode, and the following steps are carried out:
given gamma1
Where, is a block of matrices derived from the symmetry of the matrices, γ2And gamma1Representing the selected performance index, wherein I is a unit array;
according to the above LMI equationAfter positive definite symmetric matrix X, positive definite symmetric matrix M and matrix W are determined, then H2/H∞The robust controller for state feedback is as follows:
For an integrated electronic hydraulic control system, a system state space model of the integrated electronic hydraulic control system is as follows:
wherein u is1Is the output torque of the motor and is,
is x1Derivative of, y1＝Ps，θmIs the angular displacement of the rotor of the motor,
angular displacement of rotor theta for electric machinemDerivative of, PsFor servo-controlling the master cylinder pressure, PwWheel cylinder pressure for braking wheel cylinder in operating state, A1、B1And C1Is a matrix of coefficients.
For coefficient matrix A1Coefficient matrix B1And coefficient matrix C1Respectively as follows:
wherein the content of the first and second substances,
Jmis the total equivalent moment of inertia, C, of the rotating parts in the integrated electronic hydraulic control systemmIs the damping coefficient of the motor, PhIs the lead of a ball screw, msTo servo the mass of the master cylinder piston, AsTo servo the pressure area of the master cylinder piston, AwThe sectional area of a piston of a brake wheel cylinder, beta is the volume elastic modulus of brake fluid, LsFor servoing the maximum stroke of the master cylinder piston, KwEquivalent stiffness of the brake disc, LwFor the initial stroke of the brake wheel cylinder piston, rho is the brake fluid density, dpIs the diameter of the brake pipe, LpFor length of brake pipe, VhFor brake fluid viscosity, k is the linearization coefficient, CdTo control the valve flow coefficient, E is the effective restriction area of the control valve.
The invention has the advantages that: a robust controller is constructed based on a linear state space model and an augmented state space model, the influence of multiple uncertain factor disturbance such as temperature, humidity and load disturbance on a servo main cylinder is reduced due to the fact that linearization processing is adopted on a balance point, steady-state errors can be eliminated by utilizing an integral link in the augmented state space model, and the robust controller has a strong inhibiting effect on errors generated by inaccuracy and parameter perturbation.
Drawings
Fig. 1 is a schematic diagram of a specific structure of an integrated electronic hydraulic control system according to the present invention.
FIG. 2 is a flow chart of the construction of the robust controller according to the present invention.
Fig. 3 is a control block diagram of the present invention.
Description of reference numerals: 1-motor, 2-ball screw, 3-servo main cylinder, 4-control valve, 5-brake pipeline and 6-brake wheel cylinder.
Detailed Description
The invention is further illustrated by the following specific figures and examples.
As shown in fig. 1 and 3: in order to reduce the influence of uncertain factor disturbance and meet the requirement of high-performance linear braking, the invention is suitable for a master cylinder pressure robust control method of an integrated electronic hydraulic braking system, and specifically comprises the following steps:
for an integrated electro-hydraulic control system, constructing a robust controller for robust control of a master cylinder pressure of the integrated electro-hydraulic control system, wherein, in constructing the robust controller, establishing Z2Model as H2Performance index, using the output of the corresponding linear state space model of the integrated electronic hydraulic control system as H∞The linear state space model is obtained by constructing a linear processing balance point based on the system state space model of the integrated electronic hydraulic control system, the linear processing of the balance point comprises the Taylor expansion processing of a nonlinear term of the system state space model, and the micro state change near the balance point is used as a state variable;
when the integrated electronic hydraulic control system is in a braking working state, obtaining braking working parameters of the integrated electronic hydraulic control system, wherein the braking working parameters comprise state variables of micro state changes at a balance point and a master cylinder pressure micro variable quantity error of a servo master cylinder 3; the robust controller determines the control input torque of the motor 1 in the integrated electronic hydraulic control system according to the brake working parameters, so that when the output torque of the motor 1 is the determined control input torque, the master cylinder pressure of the servo master cylinder 3 in the integrated electronic hydraulic control system is matched with the master cylinder pressure reference value of the servo master cylinder 3.
Specifically, the integrated electronic hydraulic control system may adopt a conventional form, a specific implementation is provided in fig. 1, and the specific implementation of the integrated electronic hydraulic control system may be selected as needed to meet actual application requirements, which is not described herein again. In the embodiment of the invention, for the integrated electronic hydraulic control system, in order to meet the purpose of robust control, a robust controller needs to be constructed, namely the constructed robust controller is used for carrying out required robust control on the integrated electronic hydraulic control system.
In the embodiment of the invention, when the robust controller is constructed, the robust controller is establishedZ2Model as H2Performance index, using the output of the corresponding linear state space model of the integrated electronic hydraulic control system as H∞Controlling the index so as to determine H2Performance index and H∞After the indexes are controlled, the robust controller can be designed and solved by adopting the technical means commonly used in the technical field. When robust control is carried out by utilizing a robust controller, external disturbance can be overcome, and ideal output characteristics are maintained; generally, by configuration H2The performance index can enable the robust controller to have better performance, and the H is configured∞The control indexes can enable the robust controller to have better robustness.
In specific implementation, the linear state space model is constructed based on the system state space model of the integrated electronic hydraulic control system after linear processing of the balance point, and for a certain integrated electronic hydraulic control system, the system state space model of the integrated electronic hydraulic control system can be constructed by utilizing the common technical means in the technical field.
After obtaining the system state space model, determining a balance point of the system state space model, and performing linearization processing on the balance point, specifically, the linearization processing may specifically be: and (3) taking the micro state change near the balance point as a state variable, carrying out Taylor formula expansion on the nonlinear term of the system state space model, ignoring the high-order term and simplifying. For a certain integrated electronic hydraulic control system, the system state space model balance point of the integrated electronic hydraulic control system can be specifically analyzed and determined, such as the integrated electronic hydraulic control system in fig. 1, the master cylinder pressure of the servo master cylinder 3 is equal to the wheel cylinder pressure of the brake wheel cylinder 6 in the working state at the balance point. In addition, the nonlinear term of the system state space model can also be specifically determined, after the nonlinear term in the system state space model is determined, taylor expansion processing can be performed by adopting a technical means commonly used in the technical field, and when the taylor expansion processing is performed, the linear state space model can be constructed and obtained after high-order terms are ignored and simplified.
When robust closed-loop control is carried out, the braking working parameters of the integrated electronic hydraulic control system in the braking working state need to be acquired, and in specific implementation, the braking working parameters comprise state variables of micro state changes near a balance point and a master cylinder pressure micro variation error of a servo master cylinder 3; the robust controller determines the control input torque of the motor 1 in the integrated electronic hydraulic control system according to the brake working parameters, so that when the output torque of the motor 1 is the determined control input torque, the master cylinder pressure of the servo master cylinder 3 in the integrated electronic hydraulic control system can be matched with the master cylinder pressure reference value of the servo master cylinder 3.
The output torque of the motor 1 is the determined control input torque, specifically, the output torque of the motor 1 is the same as the determined control input torque, or the output torque of the motor 1 and the determined control input torque are within an allowable error range, and the allowable error range can be selectively determined according to actual needs so as to meet actual working requirements. The master cylinder pressure of the servo master cylinder 3 is matched with the master cylinder pressure reference value of the servo master cylinder 3, specifically, the master cylinder pressure of the servo master cylinder 3 is matched with the master cylinder pressure reference value of the servo master cylinder 3 to be equal, or the corresponding difference value between the master cylinder pressure of the servo master cylinder 3 and the master cylinder pressure reference value of the servo master cylinder 3 is within an allowable range, and the allowable range of the difference value can be selected according to actual needs so as to meet the requirements of actual application scenes.
The master cylinder pressure of the servo master cylinder 3, specifically, the current master cylinder pressure of the servo master cylinder 3, and the current master cylinder pressure of the servo master cylinder 3, can be detected and obtained by adopting a commonly used technical means in the technical field. The master cylinder pressure reference value of the servo master cylinder 3 can be generally given by the vehicle state; that is, when robust control is performed, the master cylinder pressure reference value is known and is related to the driving state of the vehicle, and the specific manner of determining and acquiring the master cylinder pressure reference value of the servo master cylinder 3 is consistent with the prior art, and is not described herein again.
Furthermore, an integral link for eliminating steady-state errors is added into the linear state space model to obtain an augmented state space model of the balance point;
after obtaining the space model of the augmentation state, when constructing a robust controller, the output of the space model of the augmentation state is used
As H∞And (5) controlling the index.
In specific implementation, in order to eliminate the steady-state error, an integral link can be added into the linear state space model, that is, the steady-state error can be eliminated by using the action of the integral link, and after the integral link is added into the linear state space model, the formed space model is the augmented state space model. In the embodiment of the invention, after the augmented state space model is constructed and the robust controller is constructed, the output y of the augmented state space model is taken as H∞And controlling the index.
As shown in fig. 1, the integrated electronic hydraulic control system further includes a ball screw 2, a plurality of control valves 4, and a brake pipe 5 connected to the control valves 4 in an adaptive manner, wherein an output shaft of the motor 1 is connected to a piston rod of the servo master cylinder 3 through the ball screw 2 in an adaptive manner, and a brake wheel cylinder 6 is connected to the servo master cylinder 3 through a brake pipe 5 and a corresponding control valve 4 in an adaptive manner.
In the embodiment of the invention, the motor 1 can adopt the existing common form, the specific type and the like of the motor 1 can be selected according to actual needs, and the output shaft of the motor 1 is in adaptive connection with the piston rod of the servo main cylinder 3 through the ball screw 2, so that the rotary motion of the output shaft of the motor 1 is converted into the linear motion of the piston in the servo main cylinder 3 through the ball screw 2, and the main cylinder pressure of the servo main cylinder 3 is changed. The driving mode of driving the servo main cylinder 3 to move through the motor 1 and the ball screw 2 is consistent with the prior art.
The servo master cylinder 3 may in particular take a conventional form, the servo master cylinder 3 being connected to the brake cylinders 6 via corresponding control valves 4. In fig. 1, a servo master cylinder 3 is in adaptive connection with four brake cylinders 6 through two control valves 4, wherein one control valve 4 is in adaptive connection with two brake cylinders 6 through two brake pipelines 5 respectively, that is, brake fluid passes through the control valve 4 and reaches the corresponding brake cylinder 6 through the brake pipeline 5, and pushes a piston in the brake cylinder 6 to realize braking, that is, the brake cylinder 6 in the current working state can be determined.
Specifically, the brake fluid needs to be stored in the brake line 5, and the control valve 4 is generally a commonly used solenoid valve. During braking, for the brake wheel cylinder 6 in a working state, after the pressure of the brake wheel cylinder 6 is increased, the brake caliper corresponding to the brake wheel cylinder 6 clamps the corresponding brake disc to complete braking, and the form and the process of corresponding matching of the brake wheel cylinder 6 and the brake disc through the brake caliper are the same as those of the prior art. In fig. 1, a fork-shaped circuit is adopted, and a control valve 4 controls a right front brake wheel cylinder (FR) and a left rear brake wheel cylinder (RL); the other control valve 4 controls a front left brake cylinder (FL) and a rear right brake cylinder (RR), and at this time, one control valve 4 controls two brake cylinders 6, that is, two brake cylinders 6 are simultaneously in an operating state, the wheel cylinder pressure of each brake cylinder 6 in operation is the same, and at a balance point, the wheel cylinder pressure of the two brake cylinders 6 is the same as the master cylinder pressure of the servo master cylinder 3. The wheel cylinder pressure of each brake wheel cylinder 6 in the working state can be detected by adopting a technical means commonly used in the technical field, and the specific way for determining the wheel cylinder pressure can be selected as required, which is not described herein again.
As can be seen from the above description, when constructing the robust controller, it is necessary to construct the system state space model of the integrated electronic hydraulic control system, construct the linear state space model according to the system state space model, and after obtaining the linear state space model, construct the augmented state space model. The specific process of constructing the system state space model, the linear state space model, the augmented state space model, and the robust controller in the integrated electronic hydraulic control system of fig. 1 will be described in detail below.
Further, for the integrated electronic hydraulic control system, the system state space model of the integrated electronic hydraulic control system is:
wherein u is1Is the current torque of the motor 1 and,
is x1Derivative of, y1＝Ps，θmFor the angular displacement of the rotor of the motor 1,
for angular displacement theta of rotor of motor 1mDerivative of, PsFor servo-controlling the master cylinder pressure, P, of the master cylinder 3wWheel cylinder pressure of brake wheel cylinder 6 for operating, A1、B1And C1Is a matrix of coefficients. Current torque u of electric machine 11Is the current output torque of the motor 1.
In the embodiment of the invention, the coefficient matrix A1Coefficient matrix B1And a coefficient matrix C1Respectively as follows:
wherein the content of the first and second substances,
Jmis the total equivalent moment of inertia, C, of the rotating parts in the integrated electronic hydraulic control systemmIs the damping coefficient, P, of the motor 1hIs the lead of the ball screw 2, msTo servo the mass of the master cylinder 3 piston, AsTo servo the pressure area of the piston of the master cylinder 3, AwThe sectional area of a piston of a brake wheel cylinder 6, beta is the volume elastic modulus of brake fluid, LsFor maximum stroke of the servo master cylinder 3 piston, KwEquivalent stiffness of the brake disc, LwFor the initial stroke of the piston of the brake wheel cylinder 6, rho is the brake fluid density, dpFor braking the pipe-line5 diameter, LpFor the length of the brake pipe 5, VhFor brake fluid viscosity, k is the linearization coefficient, CdE is the effective throttle area of the control valve 4 for the flow coefficient of the control valve 4.
In particular, for a certain integrated electro-hydraulic control system, the total equivalent moment of inertia J of the integrated electro-hydraulic control systemmDamping coefficient C of motor 1mLead P of ball screw 2hMass m of servo master cylinder 3 pistonsPressure receiving area A of servo master cylinder 3 pistonsSectional area A of piston of brake cylinder 6wBrake fluid bulk modulus beta, maximum stroke L of servo master cylinder 3 pistonsEquivalent stiffness K of a brake discwAnd the initial piston stroke L of the brake wheel cylinder 6wBrake fluid density ρ, diameter d of brake pipe 5pLength L of brake pipe 5pViscosity V of brake fluidhFlow coefficient C of control valve 4dAnd the effective restriction area E of the control valve 4 can be determined, in a manner known to those skilled in the art, for example, by determining the operational parameters of the integrated electronic hydraulic control system, which will not be described herein again.
For the above linearization coefficient k, there are generally:
Pswfor the purpose of determining the wheel cylinder pressure P of the brake wheel cylinder 6 in the active state for the purpose of the pressure flowing through the control valve 4 into the brake line 5wWith the pressure P flowing through the control valve 4 into the brake line 5swThen, the linearization coefficient k can be specifically determined.
Further, the linear state space model is:
where y is a small change amount of the master cylinder pressure of the servo master cylinder 3, and y is δ PsU is the current moment of the electric machine 1 relative to the equilibrium pointA small amount of change in torque, u ═ u1-ue，u1Is the current torque, u, of the motor 1eThe motor moment is a balance point;
is the derivative of x, δ θmIs the micro-variation, deltaP, of the current angular displacement of the rotor of the motor 1 relative to the angular displacement of the rotor at the balance pointsTo servo the minor variation, deltaP, of the current master cylinder pressure of the master cylinder 3 with respect to the master cylinder pressure at the balance pointwA, B and C are coefficient matrices for the minute amount of change in the current wheel cylinder pressure of the brake wheel cylinder 6 in the operating state with respect to the wheel cylinder pressure at the equilibrium point.
In specific implementation, the current angular displacement of the rotor of the motor 1 is slightly changed by delta theta relative to the angular displacement of the rotor at the balance pointmThe specific situation of (1) can refer to the calculation mode of the micro variation of the current moment of the motor 1 relative to the moment at the balance point, namely the micro variation delta theta of the current rotor angular displacement of the motor 1 relative to the rotor angular displacement at the balance pointmIs the difference between the current angular displacement of the rotor of the motor 1 and the angular displacement of the rotor at the balance point. Delta PsIs a micro variation, delta P, of the current master cylinder pressure of the servo master cylinder 3 relative to the master cylinder pressure at the balance pointwThe detailed description of the current wheel cylinder pressure of the brake wheel cylinder 6 in the operating state with respect to the minute amount of change of the wheel cylinder pressure at the equilibrium point is similar, and will not be repeated here.
In the embodiment of the present invention, the coefficient matrix a, the coefficient matrix B, and the coefficient matrix C are respectively:
wherein the content of the first and second substances,
Jmis the total equivalent moment of inertia, C, of the rotating parts in the integrated electronic hydraulic control systemmIs the damping coefficient, P, of the motor 1hIs the lead of the ball screw 2, msTo servo the mass of the master cylinder 3 piston, AsTo servo the pressure area of the piston of the master cylinder 3, AwThe sectional area of a piston of a brake wheel cylinder 6, beta is the volume elastic modulus of brake fluid, LsFor maximum stroke of the servo master cylinder 3 piston, KwEquivalent stiffness of the brake disc, LwFor the initial stroke of the piston of the brake wheel cylinder 6, rho is the brake fluid density, dpIs the diameter, L, of the brake pipe 5pFor the length of the brake pipe 5, VhFor brake fluid viscosity, k is the linearization coefficient, CdFor the flow coefficient of the control valve 4, E is the effective throttle area of the control valve 4, L0Is the initial length (in meters) of the cylindrical cavity of the servo master cylinder 3.
In the concrete implementation, during the linearization treatment, the state of the integrated electronic hydraulic control system in the balance state and the state near the balance point is analyzed. For the integrated electro-hydraulic brake system of fig. 1, one skilled in the art will appreciate that: in the balanced state, the master cylinder pressure of the servo master cylinder 3 and the wheel cylinder pressure of the brake wheel cylinder 6 are equal, and the system state variable is a constant value, that is, the above
The values are considered constant. And (3) taking a tiny variable near a balance point as a state variable, expanding a nonlinear term of the system state space model according to a Taylor formula, ignoring a high-order term and simplifying to obtain the linear state space model.
In concrete implementation, when a system state space model is obtained through modeling, b1(θm)、b2(θm)、c1(Pw) Respectively, the angular displacement theta of the rotor with respect to the motor 1mThe wheel cylinder pressure P of the brake wheel cylinder 6wRelated quantity, and the angular displacement of the rotor of the machine 1 thetamThe wheel cylinder pressure P of the brake wheel cylinder 6wAnd is an input quantity, i.e. is non-linearAn item; after linearization, b 'is obtained from the above and the concrete form of the model parameters'1、b′2And c' become angular displacements theta with the rotor of the motor 1mWheel cylinder pressure P of brake wheel cylinder 6wIndependent coefficients, thereby achieving linearization processing. The higher-order term is a term with the order greater than 1 in the expansion terms.
Further, the augmented state space model is:
wherein the content of the first and second substances,
to augment the output of the state space model,
e is the error of the micro variation of the master cylinder pressure of the servo master cylinder 3, e is r-y, r is the reference variation of the master cylinder pressure of the servo master cylinder 3,
in the embodiment of the invention, when an integration link is added to construct an augmented state space model, the state variable is specifically selected as a differential form of the original state variable. In a specific implementation, the master cylinder pressure reference value of the servo master cylinder 3 is the sum of the master cylinder pressure value of the servo master cylinder 3 at the balance point and the master cylinder pressure reference variation r of the servo master cylinder 3.
In order to servo the differential of the master cylinder pressure reference variation r of the master cylinder 3,
in order to servo the differential of the minute change amount of the master cylinder pressure of the master cylinder 3,
is the differential of the present moment of the motor 1 with respect to the minute amount of change in the moment at the balance point.
Further, when constructing a robust controller, Z is established2Model as H2The performance indexes are as follows:
wherein the content of the first and second substances,
q is a tracking performance matrix of the master cylinder pressure reference value of the reaction servo master cylinder 3, and R is an input value energy matrix of the reaction input value.
In one embodiment, J is an objective function, i.e., H2A performance index function; the tracking performance matrix Q and the input value energy matrix R are constant matrixes configured according to performance requirements, and the input values reflected by the input value energy matrix R are
As can be seen from the above description,
i.e. the derivative of the present torque change of the electric machine 1
The tracking performance matrix Q and the input value energy matrix R may be specifically based on H2The requirement of the performance index is specifically configured to satisfy H2The requirement of the performance index is the criterion, and the detailed description is omitted here.
In the embodiment of the invention, for the integrated electronic hydraulic control system, the transfer function of the integrated electronic hydraulic control system can be obtained, and further the Z under an extended state space model can be obtained2Model and perturbed closed loop transfer function G z2w2 norm of(s) | | Gz2w(s)||2And the closed loop transfer function
Infinity norm of
Wherein, | | Gz2w(s)||2Representing a disturbance to z2The 2-norm of the model transfer function,
representing perturbation to augmented state space model output
Infinity norm of the transfer function of (1), so that the solution of a robust controller can be converted into | Gz2w(s)||2<γ2，
And solving the problem.
From the above can be from: h is to be2/H∞The state feedback robust control is solved by using an LMI (linear matrix inequality) mode, and then:
given gamma1
Where, is a block of matrices derived from the symmetry of the matrices, γ2And gamma1Representing the selected performance index, wherein I is a unit array;
according to the LMI equation, after determining a positive definite symmetric matrix X, a positive definite symmetric matrix M and a matrix W, H is2/H∞The robust controller for state feedback is as follows:
In the embodiment of the invention, for a given performance index gamma1Is an empirically chosen constant, the performance index γ1Smaller means better performance, but smaller may result in no feasible solution, and can be generally determined according to actual situation. Size of unit matrix I and matrix
Matrix of
In correlation, positive definite symmetric matrices X and M are also one of the feasible solutions in the solution process, X and M are symmetric positive definite matrices, and W is a matrix. For the above-mentioned blocks of the matrix resulting from the symmetry of the matrix, e.g.
Can be expressed as:
i.e. at this time is phi2 TTherefore, the specific condition of the matrix block in the above formula is obtained specifically according to the symmetry of the matrix, and is not described herein again. Trace (M) is the trace for calculating the positive definite symmetric matrix M.
According to the LMI, a matrix W and a positive definite symmetric matrix X can be obtained through solving, and after the matrix W and the positive definite symmetric matrix W are obtained through solving, F is WX-1. From the feedback matrix F, the expression of the robust controller can be derived as:
reference is made to the above description. For robust controllers, obtaining
Then, according to the current torque u of the motor 11Adding to said
The control input torque can be obtained.
As can be seen from fig. 3, when robust control is performed by the robust controller, the master cylinder pressure minor change error e of the servo master cylinder 3 can be obtained from the master cylinder pressure reference change r of the servo master cylinder 3 and the master cylinder pressure minor change y of the servo master cylinder 3. In FIG. 3, 1/s is an integration element, and a block matrix F2And an integration link is used for processing; at the same time, using the blocking matrix F1State variables for minute state changes near the equilibrium point
And integrating the obtained x to finally obtain u as the trace variable quantity of the current moment of the motor 1 relative to the moment at the balance point. In fig. 3, the part including the coefficient matrix a, the coefficient matrix B, and the coefficient matrix C is a coefficient matrix in the linear state space model.
Claims (10)
1. A master cylinder pressure robust control method suitable for an integrated electronic hydraulic brake system is characterized in that,
for an integrated electro-hydraulic control system, constructing a robust controller for robust control of a master cylinder pressure of the integrated electro-hydraulic control system, wherein, in constructing the robust controller, establishing Z2Model as H2Performance index, using the output of the corresponding linear state space model of the integrated electronic hydraulic control system as H∞A control index, wherein the linear state space model is obtained by constructing a system state space model based on the integrated electronic hydraulic control system after linear processing of a balance point, and the linearity of the balance pointThe processing comprises the steps of carrying out Taylor expansion processing on a nonlinear term of a system state space model, and taking micro state change near a balance point as a state variable;
when the integrated electronic hydraulic control system is in a brake working state, obtaining brake working parameters of the integrated electronic hydraulic control system, wherein the brake working parameters comprise state variables of micro state changes at a balance point and a master cylinder pressure micro variation error of a servo master cylinder (3); and the robust controller determines the control input torque of the motor (1) in the integrated electronic hydraulic control system according to the brake working parameters, so that when the output torque of the motor (1) is the determined control input torque, the master cylinder pressure of the servo master cylinder (3) in the integrated electronic hydraulic control system is matched with the master cylinder pressure reference value of the servo master cylinder (3).
2. The robust master cylinder pressure control method for an integrated electronic hydraulic brake system as claimed in claim 1, wherein an integral element for eliminating steady state error is added to the linear state space model to obtain an augmented state space model of the balance point;
after obtaining the augmented state space model, when constructing a robust controller, taking the output y of the augmented state space model as H∞And controlling the index.
3. The master cylinder pressure robust control method suitable for the integrated electronic hydraulic brake system according to claim 2, wherein the integrated electronic hydraulic control system further comprises a ball screw (2), a plurality of control valves (4) and a brake pipeline (5) in adaptive connection with the control valves (4), wherein an output shaft of the motor (1) is in adaptive connection with a piston rod of the servo master cylinder (3) through the ball screw (2), and the brake wheel cylinder (6) is in adaptive connection with the servo master cylinder (3) through a brake pipeline (5) and the corresponding control valve (4).
4. The robust master cylinder pressure control method for an integrated electro-hydraulic brake system as claimed in claim 3, wherein said linear state space model is:
wherein y is the micro-variation of the master cylinder pressure of the servo master cylinder (3), and y is delta PsU is a minute amount of change in the current torque of the motor (1) relative to the torque at the equilibrium point, and u is equal to u1-ue，u*Is the current torque of the electric machine (1), ueThe motor moment is a balance point;
is the derivative of x, δ θmIs the micro-variation, delta P, of the current rotor angular displacement of the motor (1) relative to the rotor angular displacement at the balance pointsIs used for servo the micro variation of the current master cylinder pressure of the master cylinder (3) relative to the master cylinder pressure at the balance point, delta PwA, B and C are coefficient matrixes for the minute amount of change in the current wheel cylinder pressure of the brake wheel cylinder (6) in an operating state with respect to the wheel cylinder pressure at the equilibrium point.
5. The master cylinder pressure robust control method for the integrated electronic hydraulic brake system as claimed in claim 4, wherein the coefficient matrix A, the coefficient matrix B and the coefficient matrix C are respectively:
wherein, the first and the second end of the pipe are connected with each other,
Jmis an integrated type electronicTotal equivalent moment of inertia, C, of rotating parts in hydraulic control systemsmIs the damping coefficient, P, of the motor (1)hIs the lead of the ball screw (2), msTo servo the mass of the master cylinder (3) piston, AsFor servo of the pressure-receiving area of the piston of the master cylinder (3), AwThe sectional area of the piston of the brake wheel cylinder (6), beta is the volume elastic modulus of the brake fluid, LsFor the maximum stroke of the servo master cylinder (3) piston, KwEquivalent stiffness of the brake disc, LwIs the initial stroke of the piston of the brake wheel cylinder (6), rho is the brake fluid density, dpIs the diameter of the brake pipe (5), LpIs the length of the brake pipe (5), VhFor brake fluid viscosity, k is the linearization coefficient, CdFor control valve flow coefficient, E is the effective restriction area of the control valve, L0Is the initial length of the cylindrical cavity of the servo main cylinder (3).
6. The robust master cylinder pressure control method for an integrated electro-hydraulic brake system as claimed in claim 4 or 5, wherein the augmented state space model is:
wherein the content of the first and second substances,
to augment the output of the state space model,
e is the master cylinder pressure micro-variation error of the servo master cylinder (3), and e is r-y, r is the master cylinder pressure reference variation of the servo master cylinder (3),
7. the robust master cylinder pressure control method as claimed in claim 6, wherein the Z is established when the robust controller is constructed2Model as H2The performance indexes are as follows:
wherein the content of the first and second substances,
q is a tracking performance matrix reflecting a master cylinder pressure reference value of the servo master cylinder (3), and R is an input value energy matrix reflecting an input value.
8. The robust master cylinder pressure control method for an integrated electro-hydraulic brake system as claimed in claim 7, wherein H is2/H∞The state feedback robust control is solved by using an LMI mode, and the following steps are performed:
given gamma1
Where, is a block of matrices derived from the symmetry of the matrices, γ2And gamma1Representing the selected performance index, wherein I is a unit array;
according to the LMI equation, after determining a positive definite symmetric matrix X, a positive definite symmetric matrix M and a matrix W, H is2/H∞The robust controller for state feedback is as follows:
9. The robust master cylinder pressure control method for an integrated electronic hydraulic brake system as recited in any one of claims 3 to 5, wherein the system state space model of the integrated electronic hydraulic control system for the integrated electronic hydraulic control system is:
wherein u is1Is the output torque of the motor (1),
is x1Derivative of, y1＝Ps，θmIs the angular displacement of the rotor of the motor (1),
for the angular displacement theta of the rotor of the motor (1)mDerivative of, PsFor servo-controlling the master cylinder pressure, P, of the master cylinder (3)wA wheel cylinder pressure for braking the wheel cylinder (6) in an operating state1、B1And C1Is a matrix of coefficients.
10. The robust master cylinder pressure control method for an integrated electro-hydraulic brake system as claimed in claim 9, wherein the coefficient matrix a is a1Coefficient matrix B1And coefficient matrix C1Respectively as follows:
wherein the content of the first and second substances,
Jmis the total equivalent moment of inertia, C, of the rotating parts in the integrated electronic hydraulic control systemmIs the damping coefficient, P, of the motor (1)hIs the lead of the ball screw (2), msTo servo the mass of the master cylinder (3) piston, AsIs the pressure area of the piston of the servo master cylinder (3), AwThe sectional area of the piston of the brake wheel cylinder (6), beta is the volume elastic modulus of the brake fluid, LsFor the maximum stroke of the servo master cylinder (3) piston, KwEquivalent stiffness of the brake disc, LwIs the initial stroke of the piston of the brake wheel cylinder (6), rho is the brake fluid density, dpIs the diameter of the brake pipe (5), LpIs the length of the brake pipe (5), VhFor brake fluid viscosity, k is the linearization coefficient, CdTo control the valve flow coefficient, E is the effective restriction area of the control valve.
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